I'm using Flex 4. I'm trying to embed a dropdownlist into a datagrid column. When I have the drop-down list on its own, the three "tag" values (i.e. ACCOUNTS, ENQUIRY, PLAN) appear as expected. However, when the drop-down list is embedded in the column, only the "tag" value for that row appears and the anchor arrow disappears. I want the user to be able to modify existing values in the drop-down list or to enter new values, hence I left the data column to be editable. I did try setting editable="false" but then no values at all would show up.

Try to create a proper itemrenderer with File->New->MXML ItemRenderer.

Then remove the default Label in the new itemrenderer and add a dropdownlist which you then can populate with the right data, and add event handling functions to if needed. Check the documentation, you'll get good info there.